[mythtv-users] mpeg2 playback performance issue makes no sense

Cory Papenfuss papenfuss at juneau.me.vt.edu
Tue Oct 12 15:30:39 UTC 2004


> Also, I'm not sure it's really valid to simply treat a VOB file as a
> standard MPEG-2 file.  Mplayer may handle it OK because it has support
> for VOBs, but Myth's internal player may have problems.  Someone with
> more knowledge in this area may want to chime in...
>
 	"Standard MPEG2" files are a collection of streams of different 
ID's.  A sample DVD-based VOB file looked something like this (tcscan)

found ISO/IEC 13818-2 or 11172-2 MPEG video stream [0xe0]
found private_stream_1 stream [0xbd]
found AC3 audio track 1 [0x81]
found padding stream [0xbe]
found unknown stream [0xbb]
found navigation pack [0xbf]
         sequence: 720x480 16:9, 29.97 fps,  7500 kbps, VBV 224 kB , Custom 
Intra Matrix , Custom Non-Intra Matrix
end of stream reached
------------- presentation unit [4] ---------------
stream id [0xbb]   2254
stream id [0xbd]  63958
stream id [0xbe]   3120
stream id [0xbf]   4508
stream id [0xe0] 389288
463128 packetized elementary stream(s) PES packets found
presentation unit PU [4] contains 2259 MPEG video sequence(s)
Average Bitrate is 1170. Min Bitrate is 5500, max is 8000 (VBR)
---------------------------------------------------
(scan_pes.c) detected a total of 5 presentation unit(s) PU and 2645 
sequence(s)

A sample ivtv-recorded stream looks like this:
---------------------------------------------------
found ISO/IEC 13818-2 or 11172-2 MPEG video stream [0xe0]
found padding stream [0xbe]
found ISO/IEC 13818-3 or 11172-3 MPEG audio track 0 [0xc0]
end of stream reached
------------- presentation unit [37449] ---------------
stream id [0xbe]      2
stream id [0xc0]      1
stream id [0xe0]      9
12 packetized elementary stream(s) PES packets found
presentation unit PU [37449] contains 2 MPEG video sequence(s)
Average Bitrate is 1545130. Min Bitrate is 5000, max is 5000 (CBR)
---------------------------------------------------
(scan_pes.c) detected a total of 37450 presentation unit(s) PU and 112347 
sequence(s)

IIRC the 0xe0 is the video stream, and 0xc0 is the MP2 audio from ivtv.  I 
don't remember which is the AC3 stream on the VOB... probably 0xbd. 
Anyway, there *is* a difference between them, but they should probably 
play the same.


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